Monday, 22 October 2012

The SPWebCollection.WebsInfo property

Recently, while browsing some MSDN docs, I came across the WebsInfo property of the SPWebCollection class. This property is a collection of the SPWebInfo class which contains metadata about each web in the given web collection.

Methods and properties such as SPWeb.GetSubWebsForCurrentUser, SPSite.AllWebs and SPWeb.Webs, all return an object of the SPWebCollection class and the WebsInfo property can be used as a wrapper on some basic information about each web.

The properties available in the WebInfo class are:

Configuration

CustomMasterUrl

Description

Id

Language

LastItemModifiedDate

MasterUrl.

ServerRelativeUrl

Title

UIVersion

UIVersionConfigurationEnabled

WebTemplateId

So when working with the returned collection of webs, if you refer to any of the above mentioned properties, then there is no further need to open an expensive SPWeb object of that web. The value of the property is simply returned from the SPWebInfo object. Here is some code which demonstrates how to use the WebsInfo property.

Now here is where it gets interesting. After deploying the above code, I switched on my Developer Dashboard to confirm that referring to any of the properties is indeed as non-expensive as claimed. And here is what my Developer Dashboard had to say regarding the call:

So only 1 database query was made with the procedure proc_ListAllWebsOfSite. After opening this procedure in the Content Database, it contained this piece of code:

In fact, if you want to refer to any of these properties directly from the SPWeb objects of the returned webs, then also no additional call will be made to the database to fetch the properties. Here is the code to demonstrate that:

As far as you access only these properties from the SPWeb object, there will be no need to make any more calls to the database.

Now, If you want to refer to any of the other properties of the SPWeb object, things are going to get expensive. For example, if you want to refer to the SPWeb.SiteLogoUrl property, you will get the following result in the Developer Dashboard:

So as you can see SharePoint has to call the proc_GetTpWebMetaDataAndListMetaData procedure for each SPWeb object in order to return the SiteLogoUrl property.

If you use reflector or ILSpy and open the SPWeb Class in the Microsoft.SharePoint.dll , you will see that there are 2 internal methods called InitWeb( ) and InitWebPublic( ) which are responsible for initializing most of the properties of the SPWeb object. These methods in turn call the SPWeb.Request.OpenWebInternal( ) method which actually does the job of calling unmanaged code to open the expensive SPWeb object.

This was indeed a valuable learning for me as it would hugely impact the performance of my code. I hope it was a good learning for you too!